I think they will have in the ballpark of 20000 in the medium and long term, as long as they are competitive and not basket cases like The Force.
Perth generally has strong attendances for their clubs. The Eagles may have the best median home average in the AFL. Freo average over 40000. Scorchers do well, Wildcats have long led the NBL (may have been recently overtaken by the Kings).
The Force crowds reflect not just almost 20 years failure on field (somewhat by design of RA distributions) but also the wider state of the game. Doesn't help they have a vague ineffective name in both geographically identifier and (lack of) mascot.
Related and most importantly is the visibility and connection to "Super Rugby". For starters it's a stupid Mickey mouse name for supposedly the world's premier provincial Rugby competition. It's a competition that's long been unstable in its overreach, and now if in a death spiral. Crowds have fallen across the Aussie teams. 20 years ago the Waratahs were Swans sized crowds.
Rugby Union may be bigger in Perth than Rugby League, but for domestic offerings, the NRL is daylight ahead of Super Rugby in the public perception of prestige, continuity, importance to Australia's cultural fabric. I believe that will be reflected in how Perth will take to a new club that's done it's homework correctly.
Are sports teams in Perth well supported?
The Scorchers and Wildcats draw massive crowds. They've also been the most successful teams in the BBL and NBL.
On the other hand, the Force and Glory draw woeful crowds. They've also struggled over the last 20 years. Perth Glory drew better attendances in the NSL when they were the dominant team in the late 1990s and early 2000s.
The Eagles and Dockers are the oy teams that draw huge attendances, regardless of form. However, support for both clubs dropped somewhat when their onfield form hit rock bottom.
What we can take from this is form will impact how many Western Australians support a Perth-based NRL team. If it's a dud over several seasons then it will more likely than not struggle to draw 10-12k to its games.
Since 1997, at least five AwFuL clubs have drawn higher attendances than the Eagles.
The key detail is over that time the three lowest drawing clubs have been the Brisbane Lions, Gold Coast Suns and GWS Giants. Despite the money thrown at development in Brisbane and Sydney, it's produced mediocre gains.
